Utilizing an in vitro immunofluorescence phagocytosis assay for the detection of circulating
immune complexes sera from pregnant women, from women taking
contraceptive agents and age-matched controls were tested for their effect on the phagocytosis of
immune complexes by normal peripheral blood polymorphonuclear leucocytes (PMN).
Immune complexes present in the serum of a patient with seropositive
rheumatoid arthritis and heat-aggregated
IgG (
COHN fraction II) were used as substrate. A significant enhancement of the phagocytosis of
immune complexes by PMN in the presence of increasing amounts of pregnancy serum was seen using
rheumatoid arthritis serum as well as heat-aggregated
IgG. Serum from patients taking
contraceptive drugs and controls showed no effect on the phagocytosis of such complexes in vitro. These observations suggest that pregnancy serum contains factors which enhance the phagocytosis of
immune complexes possibly resulting in an increased clearance of such complexes. The commonly seen improvement of
rheumatic diseases in the course of pregnancy might at least partially be due to this mechanism.